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Results for “OPSONINS”

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At least 199 records · Page 11Linked to original sources
PubMed1975

Anti-Pseudomonas heat-stable opsonins in acute lymphoblastic leukemia of childhood.

Heat-stable opsonic activity against Pseudomonas aeruginosa and Staphylococcus epidermidis was measured in sera of 33 children with acute lymphoblastic leukemia at selected times during treatment of their disease. Compared to adults, opsonization of P. aeruginosa was normal in children tested at the time of diagnosis and before chemotherapy. Immediately after achievement of remission, opsonic activity against Pseudomonas was significantly decreased (P smaller than 0.05) compared with pretreatment activity. Activity usually returned to normal and remained so during long-term remission maintenance therapy. In children studied just prior to death from unremitting leukemia, however, anti-Pseudomonas opsonic activity was significantly decreased when compared with that of a group of children before any leukemic treatment (p smaller than 0.005). Anti-S. EPIDERMIDIS OPSONIC ACTIVITY SHOWED NO CHANGES DURING THE PATIENT'S COURSE. Decreased serum opsonic activity may significantly contribute to the increased incidence of severe Pseudomonas infections in patients with acute lymphoblastic leukemia.

Acute Disease↗
PubMed1983

Failure of fibronectin as an opsonin in the host defence system: a case of competitive self inhibition?

In the course of various clinical conditions, consumption of opsonic fibronectin is thought to impair the function of the reticuloendothelial (RE) host defence system. Despite evidence to support its central role in host defence, measurements of circulating fibronectin levels appear to have limited diagnostic or prognostic value. It seems that the problem may be more complex than a simple depletion of fibronectin. It is proposed that the structure of fibronectin can allow a condition of opsonic dysfunction to arise in certain patients, irrespective of the concentration of immunoreactive fibronectin. Fibronectin fragments bound to the target particles (fibrin aggregates, tissue debris, microorganisms) would prevent the binding of fibronectin and so inhibit phagocytosis by cells of the RE system.

Bacterial Infections↗
PubMed1970

Opsonins.

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Adult↗
PubMed1981

Augmentation of human monocyte opsonin-independent phagocytosis by fragments of human plasma fibronectin.

Human plasma fibronectin isolated by gelatin-affinity chromatography increases in a dose-dependent fashion the number of human monocytes that ingest particulate activators of the human alternative complement pathway in a fully synthetic medium. The fibronectin effect is selective for these particulate activators, does not extend to particles whose ingestion is dependent upon opsonization with IgG, and is not observed with pretreatment of the monocytes. Affinity chromatography with monoclonal antibody to plasma fibronectin of 440,000 daltons reveals that only 12-53% of the protein in a phagocytically active gelatin-affinity-purified fibronectin preparations is bound to the antibody. The protein eluted after affinity chromatography with monoclonal antibody of active preparations, which represented 10-43% of the protein applied, exhibits a 2- to 10-fold increment of activity per microgram of protein above the starting gelatin-affinity-purified material. Thus, the activity that augments the percent of human monocytes ingesting particulate activators of the alternative pathway is antigenically defined as plasma fibronectin. Preparations containing only intact 440,000-dalton fibronectin are also bound to and eluted from the monoclonal antibody, but they fail to augment phagocytosis. When inactive 440,000-dalton plasma fibronectin is subjected to limited trypsin cleavage, phagocytosis-enhancing activity develops that is bound to and elutes from the affinity column prepared with monoclonal antibody, thereby indicating that the enhancing activity of plasma fibronectin resides in cleavage fragments.

Clone Cells↗
PubMed1996

A novel human serum lectin with collagen- and fibrinogen-like domains that functions as an opsonin.

Collectins are C-type animal lectins with both collagenous and carbohydrate recognition domains and are involved in the first line host defense against pathogens. We report here a novel Ca(2+)-dependent and GlcNAc-binding lectin consisting of subunits of 35 kDa (P35) with a collagen-like sequence. When P35 is isolated from human serum, it forms a homopolymer by means of intermolecular disulfide bonding, as is the case with collectins. P35 cDNA was cloned from a human liver cDNA library, and the deduced amino acid sequence of 313 residues revealed that the mature form of P35 consists mainly of collagen- and fibrinogen-like domains. The latter contained two potential Ca(2+)-binding sites that may be involved in carbohydrate binding. The overall sequence of P35 was highly homologous to porcine ficolins alpha and beta. Northern blots of various human tissues showed that the major product of the 1.3-kilobase-long P35 transcript is expressed in liver. P35 enhanced phagocytosis of Salmonella typhimurium by neutrophils, suggesting an opsonic effect via the collagen region. P35 was found to bind to GlcNAc-conjugated bovine serum albumin, a neoglycoprotein, as well as to neoglycolipids containing complex-type oligosaccharides derived from glycoproteins, suggesting that P35 recognizes GlcNAc residues such as those found in microbial glycoconjugates and complex-type oligosaccharides. Therefore, P35 represents a new type of GlcNAc-binding lectin with structural and functional similarities to collectins involved in innate immunity.

Acetylglucosamine↗
PubMed1960

The role of opsonins in non-specific immunity.

A study of the recoveries of radioactivity, and of viable bacteria following injection of P(32)-labelled E. coli into the mouse peritoneum, has indicated that the rapid decrease in viable bacteria which occurs is largely due to peritoneal events, and not to the transport of bacteria elsewhere. The serum from mice given lipopolysaccharides 48 hours previously, when used to pretreat bacteria before intraperitoneal injection, was found to stimulate phagocytosis to a greater extent than did pretreatment with normal serum. In addition, macrophages themselves were found to be affected by contact with lipopolysaccharides, either in vivo or in vitro in such a way as to promote their phagocytic abilities. It is suggested that the provocation of non-specific immunity by bacterial lipopolysaccharides involves two facets at least; firstly, an increase in the opsonic capacity of the serum, and secondly an increase in the inherent capacity of phagocytic cells to perform this function.

Animals↗
PubMed1989

The human mannose-binding protein functions as an opsonin.

The human mannose-binding protein (MBP) is a multimeric serum protein that is divided into three domains: a cysteine-rich NH2-terminal domain that stabilizes the alpha-helix of the second collagen-like domain, and a third COOH-terminal carbohydrate binding region. The function of MBP is unknown, although a role in host defense is suggested by its ability to bind yeast mannans. In this report we show that native and recombinant human MBP can serve in an opsonic role in serum and thereby enhance clearance of mannose rich pathogens by phagocytes. MBP binds to wild-type virulent Salmonella montevideo that express a mannose-rich O-polysaccharide. Interaction of MBP with these organisms results in attachment, uptake, and killing of the opsonized bacteria by phagocytes. These results demonstrate that MBP plays a role in first line host defense against certain pathogenic organisms.

Antigens, Bacterial↗